I think you might need to clarify about regions? It's definitely not true that most restaurants across the entire US do this. Maybe you're talking about the south, where biscuits are pretty common?
– Cascabel♦Aug 16 '12 at 1:33

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I'm not sure I understand your question, could you please clarify which meanings of roll and bisquit you are using? The two I an thinking of are completely different things, it is like asking what is the difference between apples and parmesan.
– rumtscho♦Aug 16 '12 at 1:33

3 Answers
3

The principle difference between dinner rolls and biscuits is how they are assembled not how they are risen.

Dinner rolls are normal glutinous bread

With this method, wheat flour is mixed with water to form gluten. The dough is kneaded to align the gluten into sheets which can be inflated. Developing the gluten is essential to this type of dough.

When baked, this dough produces a springy sponge that is chewy and easy to slice.

Biscuits are assembled using the aptly named "biscuit method"

With this method, solid fat is cut into flour. The fat is not fully incorporated but is instead left in small pieces. Liquid is added and mixed in only briefly. Only a very small amount of gluten is formed and the fat is not homogeneously distributed in the dough.

When the dough bakes, the pockets of fat and lack of gluten produce a flaky, fragile product which is the characteristic biscuit texture.

Notes

Dinner rolls often have more fat and sugar than regular bread dough. This makes them more tender and richly flavored than regular bread.

Gluten also caused rolls and biscuits to be formed differently:

Rolls are made from balls of dough that are rolled to give them a tight skin

Biscuits are either cut into shape or spooned onto a pan

Rolls are risen with yeast, and biscuits with baking soda/powder. This does not cause the differences in texture but is a result of it.

Yeast acts slowly and, if used in biscuits, the rise time would allow gluten development which would make them less tender.

Conversely, baking soda doesn't have as much lift and wouldn't inflate a springy glutinous dough as much.

I have to disagree... If I take the ingredients for a roll and 'assemble' them 'like a biscuit' it is still a roll, using the ingredients for a biscuit and assemble them 'like a roll', it is still a biscuit. Why...because of the leavening.
– Cos CallisJun 6 '18 at 13:13

I feel like doing the experiment to prove it to you. If you take a high fat roll recipe, cut in the fat, don't knead it, and let it rise with yeast, you will get a tough biscuit. If you take a biscuit recipe and knead it thoroughly you will get a not-too-fluffy roll. The leavening type is important for the quality we expect but it doesn't define the recipe.
– SobachatinaJun 6 '18 at 13:28

Also, biscuits, with the same name and similar to modern biscuits except less fluffy, existed before the invention of chemical leavening.
– SobachatinaJun 6 '18 at 13:30

Just because you call it a 'biscuit' or a 'roll' doesn't make it so, especially when we cross culture and languages (see other conversations regarding marinade/brine). Looking at the recipe you link to when I look at the photos and examine the crumb I'm inclined to say that is a 'biscuit', but would say that those (and others) are in a "between space" where neither term is completely accurate. FWIW Webster's says a roll is "a small piece of baked yeast dough"
– Cos CallisJun 6 '18 at 14:49

Depending on what kinds of biscuits the OP has been having, they may also have a lot more fat, which can have as much an effect on flavor and texture as the leavening.
– Cascabel♦Aug 16 '12 at 17:22

1

@Jefromi, true, The fat-flour ratio is also significantly different for biscuits. Good point.
– Cos CallisAug 16 '12 at 17:43

1

Biscuits, in my experience, tend to be more crumbly (i.e. cannot be successfully sliced), while bread it more... bready?
– Adele CAug 17 '12 at 2:20

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This answer is a little misleading. Yes, rolls and biscuits are risen differently but this is not what makes the difference. The difference between them is how the fat is incorporated and how much gluten is formed. The leavening is a byproduct of this difference, not a cause.
– SobachatinaDec 21 '15 at 23:37

While the two are visually characterized by their structure, one homogeneous and the other layered, those structures are dependent on the methods of leavening.

Rolls and biscuits were developed over time to optimize the combination of ingredients and technique. Change either one and you would have something different.

A roll is alive with yeast that persists and continues to live after baking.
A kneaded roll made with chemical leavening would require much leavening be used. The flavor and texture would both be different. It would look more like swiss cheese than angle cake, be drier and have a bitter taste. After baking it would rapidly dehydrate.

A biscuit is the result of a chemical reaction that ceases when baking is complete. If yeast were simply mixed into flour along with butter, the yeast would be unevenly isolated from contact with the carbohydrates that it digests and the oxygen it requires to produce CO2. It wouldn't rise nearly as much, or as evenly. After baking yeast would survive and continue to digest flour where it was exposed to air, and quickly mold.

So rolls and biscuits are different methods of combining ingredients with different leavenings.

I'm pretty sure that the average baker's yeast doesn't survive the baking process as they die at 60c/140f.
– Catija♦Jun 4 '18 at 21:52

2

And if it didn't, the yeast wouldn't cause it to "mold"; yeasts and molds are distinct organisms. In fact, certain live yeasts would likely inhibit the growth of certain molds.
– SneftelJun 5 '18 at 6:59

How does this answer (ignoring the blatant errors) add anything that wasn't in other answers already?
– warrenJun 5 '18 at 19:45